1. Field of the Invention
The present invention relates to a display media of a particle-based display, and in particular, relates to a heat resistive particle for a particle-based display.
2. Description of the Related Art
Particle-based display (PBD) technology has drawn a great deal of attention in the display industry in recent years. Due to its wide viewing angles, low power consumption, light weight, and thinness, PBDs have widely been applied in a variety of areas, for example, in electronic readers, electronic paper, electronic tags, electronic signage, and the like. PBDs are capable of providing visual effects which are similar to that of reading paper. Different from backlight-type flat panel displays, PBDs utilize reflected ambient light from pigment particles to display content, and thus, there is no glare or other effects resulting from strong external light which may negatively affect reading. In addition, PBDs consume power only when the displayed contents are subjected to change.
A PBD includes a plurality of independently addressable display units spatially arranged in the form of a matrix. Each display unit is formed with a plurality of display cells, where each display cell is filled with pigment particles. Each display unit is disposed between a pair of opposed, spaced-apart substrates, and electrodes disposed on at least one substrate. When, by applying voltages onto the electrodes, an electric field is generated between the pair of substrates, the charged pigment particles in the cells migrate by attraction to the respective electrodes having opposite polarities. Thus, the locations of the pigment particles can be controlled by changing the polarities of the electrodes, thereby displaying images of the reflected light from the pigment particles or fluid.
Based on media that suspend/disperse the pigment particles in the cells, PBDs can be grouped into electrophoretic displays or dry powder type displays. The pigment particles for the electrophoretic displays and the dry powder type displays are made of polymer resin, which has poor heat resistive ability. Heat is usually produced during the operation of the displays. When polymer resin exists in a high temperature environment, it has some problems such as softening and deformation. A softened polymer resin has viscosity which makes pigment particles adhere with each other, causing particle aggregation. As a result, a response rate of the pigment particles to electric fields is reduced due to the particle aggregation. Furthermore, image displaying ability of the pigment particles would also be lost due to the particle aggregation, which affects the lifespan of particle-based displays.
Sun contains high energy ultraviolet (UV) light and infrared (IR) light, wherein near infrared light is the major heat source coming from the sun. When particle-based displays are operated in an outdoor environment for a long time and irradiated by the sun, the heat coming from sun is absorbed by the pigment particles. The probability that the pigment particles will soften and adhere with each other to cause particle aggregation is significantly increased when irradiated by the sun. Thus, the lifespan of the particle-based displays decreased.
Currently, one method for enhancing heat resistance of pigment particles is to increase a cross-linking density in the structure of the pigment particles. As such, the structural stability and the heat resistance of the pigment particles are enhanced. However, pigment particles with high cross-linking density have some problems when being fabricated, for example, it is difficult to control particle sizes and production yields of the pigment particles are low.